[PATCH 5.17 133/146] KVM: SVM: Flush when freeing encrypted pages even on SME_COHERENT CPUs

[Greg Kroah-Hartman]

From: Mingwei Zhang <mizhang@xxxxxxxxxx>

commit d45829b351ee6ec5f54dd55e6aca1f44fe239fe6 upstream.

Use clflush_cache_range() to flush the confidential memory when
SME_COHERENT is supported in AMD CPU. Cache flush is still needed since
SME_COHERENT only support cache invalidation at CPU side. All confidential
cache lines are still incoherent with DMA devices.

Cc: stable@xxxxxxxxxxxxxx

Fixes: add5e2f04541 ("KVM: SVM: Add support for the SEV-ES VMSA")
Reviewed-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Signed-off-by: Mingwei Zhang <mizhang@xxxxxxxxxx>
Message-Id: <20220421031407.2516575-3-mizhang@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 arch/x86/kvm/svm/sev.c |    9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -2217,11 +2217,14 @@ static void sev_flush_encrypted_page(str
 	unsigned long addr = (unsigned long)va;
 
 	/*
-	 * If hardware enforced cache coherency for encrypted mappings of the
-	 * same physical page is supported, nothing to do.
+	 * If CPU enforced cache coherency for encrypted mappings of the
+	 * same physical page is supported, use CLFLUSHOPT instead. NOTE: cache
+	 * flush is still needed in order to work properly with DMA devices.
 	 */
-	if (boot_cpu_has(X86_FEATURE_SME_COHERENT))
+	if (boot_cpu_has(X86_FEATURE_SME_COHERENT)) {
+		clflush_cache_range(va, PAGE_SIZE);
 		return;
+	}
 
 	/*
 	 * VM Page Flush takes a host virtual address and a guest ASID.  Fall